Fine, yellowish white powder, composed essentially of dicalcium phos-
phate, CaHP04, and hence mostly soluble in ammonium citrate.
Consequently, the citrate-soluble phosphoric anhydride* is determined
in these products, using the method employed with superphosphates (see
Superphosphates, observing note i on p. 130).
Any adulteration with mineral phosphate, gypsum or chalk, may be
detected as in superphosphates.
Precipitated calcium phosphate contains on an average ,|o •.|'-'% PaOB
soluble in citrate, and 2-3% P./)5 insoluble* in citrate but soluble in acids, 7.....8%
of moisture, 2-3% of chlorine (chloride resulting from the method of prepara-
tion) and small proportions of alumina,, ferric oxide and sulphates.
The most important potash fertilisers consist of <S lass furl salts, those
most used being ordinary /><>lassin-m chloride and sulphate. Use is also
made of cumulate (potassium and magnesium chlorides, with magnesium
sulphate and sodium chloride) ; ktimil (potassium and magnesium sulphates,
with magnesium and sodium chlorides) ; syfainc (sodium mid potassium
chlorides, with sulphates) ; html salt (composition similar to that of Kainit);
potash manure suits (potassium chloride with varying proportions
of magnesium sulphate and chloride, sodium chloride and calcium sulphate),
The value of these products depends naturally on their content of K,,(),
and for agricultural purposes it is sufficient to determine this by the method
given on p. 124.
Where, for special purposes, a complete analysis or at least a, knowledge
of the. content of sodium chloride is required, the following procedure is
A. Complete Analysis
This includes the following determinations :
1. Moisture,-........10 grams are healed at a dull red heat in an open plati-
num crucible for 10 minutes. If the salt contains magnesium chloride, it
is covered with a layer of ignited quicklime.
2. Insoluble Substances, too grams of the salt are dissolved in
about 400 c.c. of boiling water, the solution filtered through a. tared filter,
the residue being well washed and the filtrate made up to itiuu c.c. The
filter is then dried and weighed.
3. Sulphuric Acid, Chlorine, Lime, Magnesia. These are deter-
mined in aliquot parts of the above solution by tin- ordinary methods,
4. Alkalies.™ -loo c.c. of the solution prepared as in 4 ( 10 grams ol
substance) are introduced into a, 500 c.c. flask and treated as in /> (below).
1 More de.tailcd notices on the ;uwly.sis of potassium salts may he ft mud in sliiatyse
den <!«#>'«•/,«, by 1). Sidcrsky (I'iiris, itjui), and in ;i iiirmoir by It. Uui-mri un " MtMhodes
pourl'muily-st! des seln do potasHe," published in /»'»//. dc russni'intinn tlt'H tiiini,tl? xtit'r.,
«)I2, Vol. i!<J, p. M,|q,mind that, unlike Thomas slag, these do not contain P2O5 solpibl® int